Tracker Estimates

The tracker range is the distance from the satellite to the Earth's surface corrected for instrumental corrections such as USO frequency drift, internal path correction or Doppler correction.

The geophysical corrections are not applied to the tracker range. The AGC (Automatic Gain Control) is the gain applied on-board to the waveforms and corrected for instrumental errors.

The sigma0 scaling factor is used to compute the backscatter coefficient of the waveforms. The sigma0 scaling factor represents a backscatter coefficient for waveform amplitude equal to 1.

Table 1: AGC
PARAMETER AGC Corrected Estimate
NETCDF NAME agc_[x1]_[x2] where
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band.
DESCRIPTION AGC corrected for instrumental errors (agc_cor_[x1]_[x2])For SAR mode, the correction value is the closest in time to the reference measurement.
UNITS 10-2 dB
DATA SET AVAILABILITY Reduced: none
Standard: 1 Hz only
Enhanced: all
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: ALT_COM_AGC_01 algorithm
20 Hz Ku-band: SRAL Level-1B product
20 Hz C-band: SRAL Level-1B product
ADDITIONAL INFORMATION None
PARAMETERS RELATED Number of valid points to compute AGC (agc_num_val_[x1]_[x2])
RMS of the AGC (agc_rms_[x1]_[x2])
AGC validity flag (agc_qual_[x1]_[x2]). Flag indicating the use or not of the 20 Hz estimate of AGC in the computation of 1 Hz estimate.
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 2: Sigma0 scaling factor
PARAMETER Scaling Factor for Sigma0 Evaluation
NETCDF NAME scale_factor_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION Scaling factor for backscatter coefficient (sigma0) evaluation. This scaling factor represents the backscatter coefficient for waveform amplitude equal to 1. It is corrected for:
*AGC instrumental errors (agc_cor_[x1]_[x2])
*Internal calibration (sig0_cal_[x1]_[x2])
UNITS 10-2 dB
DATA SET AVAILABILITY Reduced: none
Standard: none
Enhanced: 20 Hz Ku and 20 Hz C-band only
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: none
20 Hz Ku-band: SRAL Level-1B product
20 Hz C-band: SRAL Level-1B product
ADDITIONAL INFORMATION None
PARAMETERS RELATED None
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 3: Tracker Range
PARAMETER Tracker Range Estimate
NETCDF NAME tracker_range_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates[x2]: Ku-band or C-band
DESCRIPTION LRM mode: tracker range corrected for: USO frequency drift (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2]), Doppler correction (dop_cor_l1b_[x1]_[x2])
SAR mode : reference range corrected for: USO frequency drift (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2])
UNITS 10-4 m. An offset of 700,000m to be added to the value read from the netCDF file.
DATA SET AVAILABILITY Reduced: none
Standard: none
Enhanced: 20 Hz Ku and C-bands
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: none
20 Hz Ku-band: SRAL Level-1B product
20 Hz C-band: SRAL Level-1B product
ADDITIONAL INFORMATION None
PARAMETERS RELATED Altitude on-board command (H0) computed with navigation/digital elevation model(h0_nav_dem_[x1]_[x2]). Units are on-board clock counter units (3.125/64x10-9 seconds).
This parameter is only available in the enhanced 20 Hz - Ku-band data set.
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services